PLAYING-THE-FIELD STUDY: UCLA researcher Martie Haselton (above) is seeking to solve the mystery of human attraction through scientific research -- and, yes, she spends more time in the lab than at happy hour.John Chapple

Cupid better brush up on his résumé: a California scientist could put him out of business permanently.

While the rest of us have (sometimes glumly) accepted that love is mysterious and unknowable, Martie Haselton, a researcher at the UCLA, has spent a career trying to understand human attraction, dissolving it to its barest essence with medical tests, scientific studies and research.

In the processes, she and her colleagues are changing what we understand about love, dating and sex.

An associate professor of communications and psychology, Haselton found that women dress differently, smell differently and talk at a slightly higher pitch when they are ovulating. Her research has revealed the reason (and time of month) women are attracted to “bad boys.”

She’s interested in how women compete with each other over men. And she and others in her field discovered that love is not a many splendored thing; it’s just an evolutionary adaptation. Like walking upright, only more exhausting.

Now Haselton is working to collect all that research — hers and others — into a meta-analysis, a kind of inventory of what we know about attraction, and what is left to uncover.

“The more insights we have, the better decisions we can make,” says Haselton, who has been married for 10 years.

While we think of ourselves as rational creatures, many of the decisions we make about the opposite sex are hardwired into us by evolutionary biology.

The guy at the bar who just doesn’t get that you’re not going home with him? Blame it on our ape ancestors: In order for the species to survive, men needed to overestimate how interested women were in them — lest they miss a precious opportunity to spread their seed, Haselton explains.

Likewise, if that cutie in the cubicle next to yours hasn’t yet noticed your Old Spice, it could be because a healthy dose of skepticism kept one of her ancestors from being dumped in a wolf-infested cave with a screaming newborn.

By understanding evolutionary biology we can begin to, if not overcome, than at least compensate for our sometimes inexplicable actions. Shunning that otherwise perfect guy because he earns less than you? Consider whether that is really a deal-breaker, or just a holdover from your berry-mashing, cave-painting days.

Haselton is sitting at a trendy bar in Los Angeles during happy hour. There are almost no men in the joint, and the clusters of women congregating around small tables seem relaxed, under-dressed and interested in little more than gossiping about office politics.

Maybe it’s too early in the evening to witness any real mating rituals. Or maybe it’s because the full moon is three weeks away.

Either way, Haselton is taking it in stride. Coming here was not her idea, after all. She performs her research in a lab, using blind studies, medical fertility tests and students as research subjects.

An Atlanta native, Haselton began her career in human attraction as a grad student at the University of Texas, studying how people make inferences about others’ thinking.

SO here she is, 10 years later, and the conversation turns to that central question she asked as a grad student all those years ago, “How do we know what we think we know?” It’s a question that echoes in all her work.

“Women notice that they feel different from day to day, but they don’t know why,” she says.

She has made a career of finding out and explaining it to them.

Clothes make the man (notice the woman): Baboons’ butts turn red when they’re in estrus, and lady chimps let their partners know they’re in the mood by presenting swollen genitalia.

But it had long been thought that the female of our species didn’t advertise fertility.

Haselton and her colleagues proved that theory wrong. Studying a group of 30 women aged 18 to 37, Haselton found that women dressed more attractively during ovulation than during points of low fertility in their cycle.

They chose more jewelry, trendier clothes and seemed to prefer skirts over pants.

The study, published in 2007 in Hormones and Behavior, was the first reported evidence that women do announce their fertility, even if they don’t realize they’re doing it.

Oh, you nasty boy: Women have been drawn to the “wrong” guys since cave days (or at least since the invention of the motorcycle), but why?

In a series of studies, Haselton and other researchers found that whom we’re attracted to depends on the time of the month.

The closer to ovulation women get, the more our sights turn from our Jack Black look-alike life partners to that doorman who reminds us of Jude Law.

The research has major implications for our high-divorce-rate society, Haselton says: If you find yourself fantasizing about the gardener, check your hormone levels. It could be that you’re ovulating — and not that you’re falling out of love with your partner.

Knowing so much about attraction is a double-edged sword. When Haselton was first introduced to the man who would become her husband, she took one look at his dashing features and wrote him off.

All her research told her that attractive men tended to be unreliable lotharios.

“I thought he was probably interested in a short-term fling,” she says. “He had to convince me.”

It took months, Haselton says, before her husband, Jim, wore her down.

“I wasn’t buying it,” she says. “When he introduced me to his parents, that’s when I knew.”

Cupid, Darwin’s little, fat, naked helper: Back in 2006, Haselton and other researchers discovered our “soul mates” are little more than people with good pheromones and even better timing and that love evolved for a simple reason: to make us settle.

Love serves as a “stop rule” to get us to end our search for a mate and begin our search for stemware.

And once we’re there, love serves as the sappy goop that binds us through thick and thin — at least until the kids are grown.

In a 2008 study, Haselton and her colleagues asked people to think about how much they love someone and then try to suppress thoughts of other attractive people.

They then ask the same people to think about how much they sexually desire their partners before trying to suppress thoughts about others.

The researchers found that love pushes out covetous thoughts better than sex does, a finding that Haselton says shows that love evolved to keep us together and keep kids safe and fed.

So, how do we fall in love? Haselton quotes the work of evolutionary psychologists Peter Todd at Indiana University and Geoffrey Miller at the University of New Mexico, who discovered that finding “the one,” is no different than solving for “X.”

The researchers used a computer simulation to determine how a person might best choose from a number of potential partners.

“The researchers found that the optimum proportion of possible mates to examine before setting your aspirations and making your choice is a mere 9 percent.

So, at a party with 100 possible mates, it’s best to study only the first nine you randomly encounter before you choose,” she wrote in New Scientist. “Examining fewer means you won’t have enough information to make a good choice, examining more makes it more likely you’ll pass the best mate by.”

The chemistry of love can help us from letting the right one get away.

“Fascinating work on genetics and mate preferences has shown that each of us will be attracted to people who possess a particular set of genes, known as the major histocompatibility complex (MHC), which play a critical role in our ability to fight pathogens,” Haselton wrote.

“Mates with dissimilar MHC genes produce healthier offspring with broad immune systems. And the evidence shows that we are inclined to choose people who suit us in this way: couples tend to be less similar in their MHC than if they had been paired randomly.”

To find the person with dissimilar MHC genes, people literally sniff each other out.

“In studies, people tend to rate the scent of T-shirts worn by others with dissimilar MHC as most attractive,” She wrote. “This is what ‘sexual chemistry’ is all about.”

Of course, evolution didn’t count on the Internet.

“In the media age and in the age of online dating, it may seem that we have more choices than we really do,” Haselton says. “We watch television and we log on to Match.com, and we see lots of availability, but in truth who is really available to us as a mate is a much smaller pool. There might be some tricks that get played on our minds.”

SNIFFING aside, Haselton’s research has some very seri ous implications: If our sexual and romantic urges can be boiled down to biology, doesn’t that take the fun out of romance?

Haselton doesn’t think so. While it’s true that a woman’s ovulation cycle might make her and any potential mate or rival around her feel a little differently, “We are not apes,” she says.

In other words, what Haselton hopes to prove in her meta-analysis is that, while our desires might come straight out of the primordial swamp, our decisions can be decidedly more modern — and more under our control.

What Haselton would like to see her work lead to a deeper under standing of communication and attraction.

“Humans are keen observers of the social world,” she says. “Part of our job is to figure out what patterns are out there, recognize that an cient biology is tuning our [feelings] and compart mentalize it. So a married woman can say, ‘Well, yes the gar dener is sexy, but I know where that comes from.’ “